Bridge scandal puts traffic studies in spotlight

Jan. 15, 2014
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Traffic builds on the approach to the George Washington Bridge in Leonia, N.J. after an automobile accident on Aug. 15, 2013. Engineers can obtain data from actual traffic events to study without the need for artificially created congestion. / Marko Georgiev, The Record, via AP

by Larry Copeland, USA TODAY

by Larry Copeland, USA TODAY

New Jersey Gov. Chris Christie's evolving scandal over the politically motivated closings of access lanes to the George Washington Bridge in September has thrust into the national conversation this ever-present, but seldom discussed, phenomenon of modern transportation.

If you drive regularly, chances are excellent that you've been a participant in a traffic study."Tens of thousands" of traffic studies are done annually in the USA, estimates David Schrank, a research scientist at the Texas Transportation Institute at Texas A&M University in College Station.

"There are umpteen different reasons why you would want to study traffic or learn something about it," he says.

Among those reasons:

â?¢ Traffic studies are routinely required for many new proposed development projects. The Institute of Transportation Engineers recommends that a traffic impact study be conducted whenever a proposed development will add 100 or more trips during the peak hour on adjacent roads or at the development. Local jurisdictions sometimes have their own, separate guidelines.

â?¢ Traffic studies are typically required for new projects or developments that have to go through an environmental review process, or for proposed developments that face opposition from a neighborhood group.

â?¢ Traffic studies are also done along specific highway corridors. This can be for things such as timing traffic signals or planning turn lanes or other traffic management options.

New Jersey officials initially said that they closed some access lanes to the George Washington Bridge between New Jersey and New York as part of a traffic study. Last week, Christie fired his deputy chief of staff, Bridget Anne Kelly, after the release of documents showing she was aware of the closings before they occurred. Press reports indicate the closings were meant as political payback to Fort Lee Mayor Mark Sokolich, a Democrat who did not endorse Christie for re-election.

It is unclear whether a traffic study was actually being conducted at the bridge during the lane closures, an incident that is under investigation.

Michael Sanderson, president of Sanderson Stewart, a regional engineering and planning firm based in Billings, Mont., and a former board member of the Institute of Transportation Engineers, says "it's almost a certainty" that anyone who drives regularly has participated in a traffic study. "You've almost certainly been observed, counted or your speed recorded as part of a traffic study, and you didn't have any knowledge of it," he says.

"Most of the time, you look at what you expect the future to look like," says Schrank, who says traffic studies from the states are part of TTI's Annual Urban Mobility Report, which measures congestion around the nation.

Typically, the traffic engineering department of a city, state or county, or a firm it hires, "will do what's called a screen line. They draw an imaginary line around the city, and everything that crosses that line, they count," says Alan Pisarski, author of Commuting in America, the comprehensive periodic examination of the nation's commuting patterns.

Sanderson says information is gathered either manually, "by a traffic engineer or technician sitting along a road with a clipboard, actively recording what they see," or by automated equipment, such as video data collection or sensors in the roadway.

The idea of someone standing on the side of the road counting cars "is so two years ago," says Jamie Holter, a traffic analyst with INRIX, a Kirkland, Wash.-based provider of traffic data that works with government agencies and others doing traffic studies. "With Big Data, you don't need to do that anymore. That said, many governments take a belt-and-suspenders approach to traffic studies. They will use INRIX data, but may also still send an intern out to stand on an overpass or at a corner in an orange vest with a clipboard and a clicker to count cars."

She delved into INRIX data that is routinely gathered on thousands of roads in the USA to see how the Sept. 9 bridge closure impacted traffic.

According to Holter's analysis, congestion on northbound Interstate 95 south of the George Washington Bridge more than doubled during the morning commute when two of the three lanes were closed. Travel times that day increased significantly from typical travel times at 7:45 a.m. and remained unusually heavy until 10:30 a.m.

Holter, Schrank, Pisarski and Sanderson all say it would have been standard protocol to inform the public of any traffic study expected to cause that kind of disruption. "If we were going to do a traffic study that involved significant impact of the traveling public, the agencies we work with would require us to inform the public," Sanderson says.